6.15-stable review patch. If anyone has any objections, please let me know.
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From: Kees Cook kees@kernel.org
[ Upstream commit ee4cf798202d285dcbe85e4467a094c44f5ed8e6 ]
When gmin_get_config_var() calls efi.get_variable() and the EFI variable is larger than the expected buffer size, two behaviors combine to create a stack buffer overflow:
1. gmin_get_config_var() does not return the proper error code when efi.get_variable() fails. It returns the stale 'ret' value from earlier operations instead of indicating the EFI failure.
2. When efi.get_variable() returns EFI_BUFFER_TOO_SMALL, it updates *out_len to the required buffer size but writes no data to the output buffer. However, due to bug #1, gmin_get_var_int() believes the call succeeded.
The caller gmin_get_var_int() then performs: - Allocates val[CFG_VAR_NAME_MAX + 1] (65 bytes) on stack - Calls gmin_get_config_var(dev, is_gmin, var, val, &len) with len=64 - If EFI variable is >64 bytes, efi.get_variable() sets len=required_size - Due to bug #1, thinks call succeeded with len=required_size - Executes val[len] = 0, writing past end of 65-byte stack buffer
This creates a stack buffer overflow when EFI variables are larger than 64 bytes. Since EFI variables can be controlled by firmware or system configuration, this could potentially be exploited for code execution.
Fix the bug by returning proper error codes from gmin_get_config_var() based on EFI status instead of stale 'ret' value.
The gmin_get_var_int() function is called during device initialization for camera sensor configuration on Intel Bay Trail and Cherry Trail platforms using the atomisp camera stack.
Reported-by: zepta z3ptaa@gmail.com Closes: https://lore.kernel.org/all/CAPBS6KoQyM7FMdPwOuXteXsOe44X4H3F8Fw+y_qWq6E+Odm... Fixes: 38d4f74bc148 ("media: atomisp_gmin_platform: stop abusing efivar API") Reviewed-by: Hans de Goede hansg@kernel.org Link: https://lore.kernel.org/r/20250724080756.work.741-kees@kernel.org Signed-off-by: Kees Cook kees@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- .../staging/media/atomisp/pci/atomisp_gmin_platform.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c index e176483df301..b86494faa63a 100644 --- a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c +++ b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c @@ -1358,14 +1358,15 @@ static int gmin_get_config_var(struct device *maindev, if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) status = efi.get_variable(var16, &GMIN_CFG_VAR_EFI_GUID, NULL, (unsigned long *)out_len, out); - if (status == EFI_SUCCESS) + if (status == EFI_SUCCESS) { dev_info(maindev, "found EFI entry for '%s'\n", var8); - else if (is_gmin) + return 0; + } + if (is_gmin) dev_info(maindev, "Failed to find EFI gmin variable %s\n", var8); else dev_info(maindev, "Failed to find EFI variable %s\n", var8); - - return ret; + return -ENOENT; }
int gmin_get_var_int(struct device *dev, bool is_gmin, const char *var, int def)